1. Field of the Invention
The invention relates to a sewing machine which stretches a work fabric on a cylindrical frame.
2. Description of the Related Art
A cylindrical sewing frame is commonly used in embroidering a tube-like piece of fabric such as material for socks and wrist bands. The cylindrical frame is placed to cover the outside of the cylinder bed. The cylindrical frame is driven in the axial direction and around its axis. A device for a sewing machine is disclosed in International Patent Publication Number WO00/53836 that is able to support the tube-like work fabric close to the point of stitching. The cylindrical frame of this device has a small diameter and guides the fabric near the outside of the cylinder bed.
The device of the prior art comprises a detachable guiding member 102 at the front end of a cylinder bed 101 as shown in FIG. 11. A cylindrical frame 104 is equipped with a sewing window 103. The guiding member 102 has an annular shape with a diameter that is slightly smaller than the inner diameter of the cylindrical frame 104 and is provided integrally with a needle plate part 105 and a mounting plate 106. The mounting plate 106 is located at the top specifically for the cylindrical frame 104. In sewing a tube-like piece of work fabric, the needle plate 105 supports the work fabric as the plate is exposed through the sewing window 103 while the inside of the guiding member 102 guides the cylindrical frame 104 parallel to the cylinder bed.
However, the needle plate part 105 built specifically for a cylindrical frame is provided as an integral part of the guiding member 102 in the sewing machine of the prior art. Therefore, it is necessary to replace the needle plate 105 to replace the cylindrical frame 104 with a different frame such as a rectangular frame, an annular frame, etc. The needle plate 105 is replaced by removing the guide member 102 and mounting another needle plate on the cylinder bed 101.
The present invention provides a sewing machine which does not require replacing the needle plate in order to replace a frame. The cylindrical frame is guided with a member independent of the needle plate so that the needle plate can be permanently installed for use with all kinds of sewing frames.
The cylindrical frame covers the outside of the cylinder bed and is driven in its axial direction and around its axis so that the work fabric stretched over the cylindrical frame can be stitched. A partial cylindrical surface on the guide member is concentric with the cylindrical frame and is located near the inner surface of the cylindrical frame. A bobbin case and a needle plate are located at the front end of the cylinder bed. A guide member is mounted on the cylinder bed located below the needle plate and guides the cylindrical frame from the inside.
The design of the guide member is not limited to a specific configuration or composition. The guide member can be constructed to prevent vibrations by enhancing the strength of the mount and can have a large area on the partial cylindrical surface. Specifically, the guide member can be formed in an open-ended rectangular shape comprising two side walls connected at the rear end and an open front end. The connecting part of the guide member is mounted on the cylinder bed, and a bobbin case is installed between the two side walls. A partial cylindrical surface is formed on the outside of the side walls.
In this case, a protection cover can be provided on the guide member to prevent the bobbin case, which is a revolving member, from being exposed when the cylindrical frame is not in use. Additionally, the cover can be used as a guide for the cylindrical frame. Specifically, the protection cover can protect the bobbin case from underneath and is mounted detachably on the guide member so that it does not hinder the replacement of the bobbin. A partial cylindrical surface can be provided on the protection cover to have a curvature approximately equal to the curvature of the partial cylindrical surface of the guide member.
The needle plate can be prevented from catching the work fabric that is stretched over the cylindrical frame and can have a sufficiently wide area for supporting the work fabric. Specifically, a curved surface can be provided to face the inner surface of the cylindrical frame at the left and right shoulders of the needle plate respectively.